The present invention relates to an inkjet recording head that applies pressure to eject ink accommodated in an ink cavity by deforming a piezoelectric element in accordance with input signals.
As depicted in FIG. 1, one known example of a drop-on-demand (DOD) type inkjet recording head comprises, a channel plate 10 having an ink cavity 12 and ink discharge port 14, a panel 16 covering the ink cavity 12, a piezoelectric element 18, a substrate 20 to support piezoelectric element 18, and an adhesive 24 for attaching the piezoelectric element 18 to the panel 16. In this recording head, the ink 22, which is accommodated in the ink cavity 12, is subjected to pressure so as to be discharged from the ink discharge port 14 via the deformation of panel 16 in accordance with the deformation of piezoelectric element 18. As a result, it is necessary that the deformation of piezoelectric element 18 is reliably transmitted to the panel 16, and subsequently, to the ink 22 accommodated in the ink cavity 12. Therefore, the piezoelectric element 18 is fixedly attached to panel 16 by an adhesive 24.
The above-described inkjet recording head, however, requires a degree of durability so that the piezoelectric element 18 does not separate from the panel 16 under continuous oscillation, for example, 4 KHz per 80 hrs (about 1xc3x97109) or more. Therefore, such an inkjet recording head has a disadvantage because sufficient durability cannot be obtained simply by an application of an adhesive between the piezoelectric element 18 and the panel 16.
The inkjet recording head""s durability can be increased to a certain degree by increasing the thickness of the adhesive 24. However, this is not advantageous because the deformation of piezoelectric element 18 is absorbed by the adhesive 24 when the thickness of adhesive 24 is increased. Consequently the discharge force and pressure applied to ink 20 are reduced.
FIG. 2 is a table that shows the results of analysis of the relationship between displacement loss and adhesive thickness and amount of displacement loss using a finite element method. In particular, the table shows the amount of displacement for various thicknesses of adhesive at the contact area (point a, FIG. 1) between the adhesive 24 and the panel 16, and the average amount of displacement at other contact areas (center: point b; edge: point c; midpoint between point b and point c: point d) between the adhesive 24 and the panel 16. Also, FIG. 2 shows the percentage of displacement loss relative to the amount of displacement loss of the panel, and the average amount of displacement loss of the piezoelectric element at various adhesive thicknesses (5, 25, and 50 xcexcm). As can be clearly understood from Table 1, displacement loss increases in conjunction with the increase in the adhesive thickness, thereby reducing the discharge force of ink 22. (The aforesaid analysis assumes that the adhesive has a Young""s modulus of 30 kgf/cm2.)
The inkjet recording head of the present invention has an oscillating member attached to a mounting member by an application of adhesive to the opposing surfaces of these members, wherein the adhesive on the external surfaces of the oscillating member and the mounting member forms a chamfer.
Furthermore, the inkjet recording head of the present invention is formed attaching an oscillating member to a mounting member adheres an oscillating member and mounting member by applying adhesive to at least a surface of the oscillating member or the mounting member, and thereafter pressing together the oscillating member and the mounting member so as to cause adhesive to emerge from the adhering surfaces to attach the members together.
According to the aforesaid inkjet recording head, opposed surfaces of an oscillating member and a mounting member are fixed to one another with adhesive, and a chamfer is formed in the adhesive that emerges from between the surfaces of the oscillating member and the mounting member at the adjacent external surfaces, so that the oscillating member and the mounting member have areas of attachment that extend beyond the area of attachment that exists between the opposed surfaces. This arrangement provided an advantage in that the adhesion strength and separation resistance between the oscillating member and the mounting member are improved. Furthermore, the absorption of oscillation of the oscillating member by the adhesive is suppressed to a lower limit by reducing the thickness of the adhesive by the aforesaid arrangement.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying figures.